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Ecosystem MCQs for MDCAT Practice

Biology section, Ecosystem chapter. Up to eight free sample questions, each with the correct answer and a worked explanation. The full chapter opens in the app.

The bank has 211 active questions on this chapter. Your first 500 practice attempts are free, and every attempt includes a worked explanation.

  1. Question 1
    Which of the following statements is most consistent with the interactive hypothesis?
    • Communities lack discrete geographic boundaries
    • Species are distributed independently of other species
    • The community functions as an integrated unit (correct answer)
    • The composition of plant species seems to change on a continuum
    Correct answer: C
    The interactive hypothesis views ecological communities as cohesive units where species interactions shape their overall structure and function.
  2. Question 2
    Which ecosystem has the maximum biomass?
    • Grassland ecosystem
    • Pond ecosystem
    • Lake ecosystem
    • Forest ecosystem (correct answer)
    Correct answer: D
    Forests, with their abundant, long-lived producers like trees, possess the greatest total mass of living organisms (biomass) compared to other ecosystems.
  3. Question 3
    The most appropriate method for estimating a population of a fixed plant species would be:
    • The random quadrant method (correct answer)
    • The ‘capture-recapture’ method
    • Estimating the percentage cover of the species
    • Drawing a line transect
    Correct answer: A
    The random quadrant method is best for estimating sessile plant populations by sampling representative areas and extrapolating.
  4. Question 4
    The distinct levels or links of food chain are called
    • Food web
    • Energy pyramid
    • Food chain
    • Trophic level (correct answer)
    Correct answer: D
    Understand that 'trophic level' refers to the specific position an organism occupies in a food chain, indicating its feeding relationship and energy transfer step.
  5. Question 5
    Succession is a kind of
    • Community relay (correct answer)
    • Population relay
    • Ecosystem relay
    • Biosphere relay
    Correct answer: A
    Ecological succession describes the gradual replacement of one species community by another over time in a given area.
  6. Question 6
    In Nitrogen cycle, conversion of Nitrates into nitrogen is termed as
    • Ammonification
    • Assimilation
    • Nitrification
    • Denitrification (correct answer)
    Correct answer: D
    The conversion of nitrates back to atmospheric nitrogen gas in the nitrogen cycle is called denitrification. This process is crucial for replenishing atmospheric N2.
  7. Question 7
    To measure the population density of monarch butterflies occupying a particular park, 100 butterflies are captured, marked with a small dot on a wing, and then released. The next day, another 100 butterflies are captured, including the recapture of 20 marked butterflies. One would correctly estimate the population to be:
    • 20
    • 100
    • 200
    • 500 (correct answer)
    Correct answer: D
    Estimate monarch butterfly population using the capture-recapture method. The ratio of marked to total recaptured butterflies estimates the proportion of marked individuals in the entire population.
  8. Question 8
    In which of the following habitats would you expect to find the largest number of K-selected individuals?
    • A recently abandoned field in Ohio
    • A newly emergent volcanic island
    • South Florida after a hurricane
    • The rain forests of Brazil (correct answer)
    Correct answer: D
    K-selected species thrive in stable environments with high competition, favoring traits like slow reproduction and parental care, making rainforests the ideal habitat.

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Read the full Ecosystem chapter notes: Ecosystem notes. Or browse every chapter.